[llvm] [TTI] Don't drop VP intrinsic args when delegating to non-vp equivalent (PR #147677)

[Luke Lau via llvm-commits]

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lukel97 wrote:

IIUC the type based costing is needed for places like the LoopVectorizer where we need to cost things that don't yet have `Value`s materialised, e.g. VPRecipeBase::computeCost. 

The value based costing is used by other transforms that actually have a `Value` at hand, e.g. SLPVectorizer/LoopUnroll/VectorCombine etc. 

And for some types of intrinsics and instructions, knowing the value of an operand can actually make the cost more accurate, e.g. if you know the index of a insertelement or the mask of a shufflevector, it can be much cheaper.

https://github.com/llvm/llvm-project/pull/147677